The goal of this project is to identify the genetic basis of infantile neuroaxonal dystrophy (INAD), an autosomal recessive disorder characterized by progressive motor and sensory impairment. The key pathologic feature of this form of neuroaxonal dystrophy is the widespread distribution of distended axons throughout the central and peripheral nervous systems. Defective retrograde axonal transport is a hypothesized mechanism leading to the INAD phenotype; however, the molecular defect in INAD remains unknown. By identifying a gene or genes for this fatal childhood disorder, we can offer diagnostic molecular testing and begin to investigate disease pathogenesis as a step towards developing rational therapeutics. We have established two unique resources that will accelerate disease gene discovery in humans and mice with INAD. First, we maintain the largest worldwide collection of phenotype data and DNA samples from INAD families, with which we have mapped a major gene (INAD1) for this disorder using linkage analysis. Second, we have established a colony of mutant mice with early-onset neurodegenerative disease and pathologic changes identical to those seen in humans with INAD. This sporadic mutant has been crossed to a genetically distinct strain in order to map and isolate the defective murine gene. Studies in these mice will complement those in humans and extend our knowledge of the molecular basis of the neuroaxonal dystrophies. We will use these resources to achieve our specific aims to: 1) identify the human INAD1 gene and analyze INAD pedigrees for disease-causing mutations; 2) identify the disease gene in a mouse model of INAD; and 3) initiate structural and functional characterization of the INAD genes and their protein products.